GB835587A - Improved continuous polymerization process - Google Patents

Abstract

In a continuous polymerization process employing a two-component catalyst the polymerization is carried out in two or more stages in separate vessels and after the first stage only one of the catalyst components is added afresh together with further monomer.ALSO:Olefines are polymerized in a continuous process wherein the olefines and inert liquid diluent are introduced to a first polymerization zone together with a polymerization catalyst obtained by mixing a reducing aluminium compound with a reducible metal compound in an inert liquid diluent, a portion of the resultant polymerization mixture is withdrawn continuously and passed to at least one further polymerization zone to which additional olefines and reducing metal compounds are also continuously introduced and a portion of the resultant polymerization mixture is continuously withdrawn from the further polymerization zone and passed to a separation zone for recovery of the polymer. The polymerization mixture is maintained in both the first and further polymerization zones at 100 DEG to 200 DEG F. and at 1-20 atmospheres, the average residence time in the first zone being 0.5-4 hours and in the further reaction zones, 0.5-2 hours. The olefin is preferably purified from catalyst poisons and may be ethylene, propylene or butylene and these may be copolymerized with one another or with other low molecular weight olefins or diolefines. The reducing aluminium compound is an aluminium hydride or an organo-aluminium compound, e.g. aluminium trimethyl, triethyl, triisopropyl, triphenyl, diethyl bromide, diethyl chloride, diphenyl bromide or diphenyl chloride, ethyl aluminium dihydride, diethyl aluminium hydride or ethoxy aluminium diethyl. The reducible metal compound is of a metal of the A sub-groups of groups 4, 5 or 6 of group 8 of the Periodic Table, e.g. titanium, zirconium, thorium, uranium or chromium and may be a chloride e.g. titanium tetrachloride, bromide, oxychloride, complex fluoride, oxide, hydroxide, alcoholates, acetates, benzoates or acetyl acetonates. The inert liquid diluent is preferably an hydrocarbon or halogenated hydrocarbon such as pentane, hexane, heptane, octane, nonane, decane, benzene, toluene, chlorobenzene or light petroleum. Many details of the catalyst preparation, e.g. temperature and residence time, and of the polymerization, e.g. concentration of the various components, and other conditions are given. The polymer produced may be washed with butyl alcohol or acetone to remove metal contaminant. Polyethylene prepared by this process has a low ash content and may be used as a film-forming material, lubricant additive, or in the formation of moulded or injected plastics.